SSL certs on Multisite with domain mapping plugin


I would love to know your thoughts on what SSL cert would be good for securing my entire network.

I am gradually migrating over to the network and estimate I would have 30 individual client sites on it using the domain mapping plug in.

I am trying to secure the entire network under 1 SSL cert as an added benefit to clients but would love to know what would work best and what you think would work well… or even a recommended solution?

I was looking at something like this and wondered whether it would work

Thanks again